toon-format

Skill by ara.so — Daily 2026 Skills collection. TOON is a compact, human-readable encoding of the JSON data model that minimizes tokens for LLM input. It combines YAML-style indentation for nested objects with CSV-style tabular layout for uniform arrays, achieving ~40% token reduction while maintaining or improving LLM comprehension accuracy. TOON encodes scalars the same way as YAML — unquoted when unambiguous: Square brackets declare the array length, values are comma-separated: Curly braces declare the field headers; each subsequent indented line is a row: Values containing commas, colons, or newlines are quoted: Wrap them in double quotes in your TOON string, or ensure encode() handles it automatically: TOON uses unquoted values for numbers and booleans. Ensure your data uses proper JS types before encoding — don't pass "95000" (string) when you mean 95000 (number): Add a brief TOON format explanation to your system prompt: Common mistakes in hand-written TOON: - Missing length declaration: items{id,name}: → must be items[2]{id,name}: - Inconsistent indentation (mix of tabs/spaces) - Unquoted values containing : as first character - Official Specification (SPEC v3.0) - npm package: @toon-format/toon - Online Playground - GitHub Repository